Crude oil in water emulsions can be found in all stages of production, transportation and processing of petroleum industry. An emulsion is defined as a system in which a fluid is relatively dispersed or distributed in the form of droplets (dispersed phase) in another immiscible liquid (continuous phase). The water-in-on (W/O), oil-in-water (O/W) and more complex emulsions are formed during the production of crude oil, which is often accompanied by water, and their transportation by pipeline. The dispersion of droplets of water in oil or oil in water is to be formed by the simultaneous action of sufficient mixing energy (U.S. Pat. No. 5,100,582) and by the presence in the oil of an emulsifying agent or external addition of them.
The emulsifying agents are chemicals that show surface activity reducing the surface tension of the interface when another phase is present. Emulsifying agents are also called surfactants. They are also characterized by a double affinity conferred by their molecular structure with an amphiphilic character, a part of the molecule is hydrophilic (polar character) or soluble in water and the other is lipophilic (non-polar character) or soluble in oil or non-polar solvents. The non-polar counterpart of the molecule generally is formed from a long alkyl chain. This type of structure enables them to be adsorbed and placed on the water/oil and oil/water interface, forming aggregates whose hydrophilic portions are oriented towards the aqueous environment and the hydrophobic fractions to the oily environment, decreasing then the interfacial or surface tension which allows the formation of the emulsion.
In crude oil, there are naturally occurring components that act as emulsifiers, which are located in the polar crude oil fraction, such as asphaltenes, resins, soluble organic acids (naphthenic acids). These compounds are the major constituents of the interfacial film surrounding the droplets of water, lowering the interfacial tension and preventing droplet coalescence, giving natural stability to emulsions of crude oil.
In the petroleum industry, the typical emulsions encountered are water droplets dispersed in the oil phase and called as W/O emulsion or direct emulsion. The remaining amount of emulsified water ranges from about 1 to 60% volume. In crude medium to light (>20° API), emulsions typically contain from 5 to 20% volume of water, whereas in heavy oil (<20° API) are often in the range of 10 to 35% water (Manning F S, Thompson R E, Oilfield processing. Volume 2 Crude oil, Penn Well Publishing Company, 1995).
Moreover, the formation of relatively stable O/W emulsions from heavy, extra-heavy crude oil, bitumen and shale oil is a recurring technological alternative for improving the flowability of such oils, since its specific gravity and high viscosity make difficult their transportation and further processing. High viscosity and density are mainly due to the presence of asphaltenes in concentrations which can reach 20% by weight. The specific risks during transportation of heavy oils by pipeline are high pressure drops, plugging and blockage, causing stoppages or decline on production. Conventional technology for extraction and transportation are frequently not suitable for transporting such heavy crude oils.
An effective method for reducing the viscosity of heavy oils is the formation of O/W emulsions known as inverse emulsions with the aid of an emulsifying agent. These kinds of emulsions are commonly not formed spontaneously and to ensure emulsion stability during transport in the pipeline it is necessary to add emulsifiers (usually surfactants). The surfactants selected should allow the formation as a sufficient stable emulsion for their transportation by pipelines and after that, an easy process of breaking the emulsion in the refinery and the recovery of water-free crude oil. The emulsions prepared for pipeline transport contain about 70-75% oil and the balance of water.
The formation of aqueous emulsions is useful for the transportation of crude oil. However, water should be separated before refining the crude oil due to economic and operational reasons. The emulsion breaking is a critical step in the production of crude oil, both to meet production targets and delivery specifications to processing centers. therefore, it is important to develop formulations of demulsifier agents to achieve adequate separation of the water present in the crude oil.
Aggregation, coalescence and sedimentation of crude oil must occur for breaking O/W emulsions and separation of crude oil and water. Commonly, this is achieved by methods including thermal, mechanical, chemical and electric processes (Gafonova, O. V.; Harvey, W. Y.; J. Colloid Interface Sci. 2001, 241, 469-478).
Chemical demulsification is the preferred method applied to the treatment of W/O and O/W emulsion and includes the use of chemicals (demulsifiers), which are also surface active agents which promote the process of emulsion breaking. The stability of an emulsion is strongly affected by the nature of the interfacial film and surfactant adsorption mechanisms. The most common application of the demulsification process in refineries includes the combination of heat and chemicals to neutralize and eliminate the effects of the natural emulsifying agents (Grace, R., Advances in Chemistry Series, 1992, 313-339) usually assisted by electrostatic dehydrators.
The role of the demulsifiers is to destroy the protective action of the hydrophobic film formed by emulsifier agents and allow the coalescence of the water droplets. The demulsifiers working with good efficiency for a given emulsion, may be totally ineffective in another. Typically, surfactants are classified by their ionization state in an aqueous phase as anionic, cationic and nonionic surfactants (U.S. Pat. No. 6,294,093).
Most of commercial demulsifiers have been mostly designed to break W/O emulsion, which is the type of emulsion naturally occurring during crude oil production, and are generally of the non-ionic type surfactant formulated with polymeric chains of ethylene oxide and propylene oxides, ethoxylated phenols, ethoxylated alcohols and amines, ethoxylated resins, polyhydric alcohols and salts of sulfonic acids, among others (Kokal, S L. Petroleum Engineering. Vol. 1, Society of Petroleum Engineers, 2006). Frequently, demulsifier formulation consist of a mixture of several basic commercial agents dissolved in an organic solvent, such as aromatic naphtha, benzene, toluene or isopropyl alcohol, among others.
It is known that the combination of polar amino acids (hydrophilic portion) containing non-polar (hydrophobic) long alkyl chains produces amphiphilic molecules with high surface activity and rapid biodegradation, which make them acceptable from an environmental point of view and for this reason in recent years have taken great interest. Literature reports the experimental and commercial synthesis of short-chain amino acids from aspartic acid, glutamic acid, arginine, alanine, glycine, leucine, proline, serine and protein which have been used as surfactants (Nnanna, I. A.; Xia, J. Protein-based surfactants, synthesis, physicochemical properties and applications. Marcel Dekker, 2001).
The first applications of amino acid-based surfactants was described for preserving drugs since these compounds were effective against various bacteria and viruses that cause diseases (Infante, M R., Perez, L., Pinney, A.; Clapes, P.; Moran, M C, Amino acid-based surfactants. In Novel Surfactants, Ed K. Holmberg 2003, 193-216). With the reduction of production costs, amino acid-based surfactants have been used as additives for food, flavor, and pharmaceutical applications (Takehara, M. Colloids Surf., 1989, 38, 149-167), and extensive research has been done for their application of cosmetic manufacture (Husmann, M. SOWF J. 2008, 134, 34-40). However, these publications do not disclose their use as demulsifiers for crude oil in water emulsions in the oil industry.
The U.S. Pat. No. 6,211,141 discloses the use of glycine as part of the formulation of a detergent powder. U.S. Pat. No. 7,662,225 discloses the use of glycine betaine amides for the formulation of surfactants to form stable aqueous emulsions of bitumen for the production of road surfaces.
In U.S. Pat. No. 7,829,521, the composition of surfactants made from esters or amides of glycine betaine is described and their application is related to the cosmetic area in the formulation of liquid soap, foam, shower gel and shampoo.
The referred patents correspond to the application of betaine derivatives, salt of (carboxymethyl)trimethylammonium or trimethylglycine in the formulation of detergents or cleaning agents or for the formation of aqueous emulsions of bitumen used in paving roads.